Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 262024

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
324 PM CDT TUE JUL 26 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 315 PM CDT Tue Jul 26 2016

The short term concerns are timing and severity of convection
tonight into Wednesday.

Current water vapor imagery showing a couple of short waves
affecting the region this afternoon.  One to the north...which
continues to generate some isolated convection...north of the cwa.
THe other...stronger wave is over South Dakota and is generating
more widespread convection into eastern South Dakota.  Latest
mesoscale analysis is showing MLCAPE to 3000 j/kg in the northern
cwa. This region remains under at least some weak moisture transport
and waa under the right entrance region of 30h jet across southern
Canada. It should force at least scattered convection along the weak
frontal boundary into this evening.  Isolated severe is
possible...mainly because of high CAPE/DCAPE into the evening.

Farther west...stronger deep layer shear exists and the Dakotas
convection may develop into a MCS this evening and drop east
southeast into southwest Minnesota late. It still looks like much of
the far southern cwa will remain dry overnight...until the trough
and surface low moves in on Wednesday.  We will continue the likely
pop trend as it moves across the area. This along with more cloud
cover should limit overall temperature rises...especially to the
west...where they should remain in the 70s Wednesday afternoon.
Although shear will be greater...any severe convection will be
highly conditional and on amount of heating/destabilization...and
that currently looks limited.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 315 PM CDT Tue Jul 26 2016

Main forecast concerns is timing of when or how long the
precipitation lasts Wednesday night/Thursday, and the heat
returning next week.

Wednesday night precipitation chances will depend on the strength
of the frontal boundary and how far south-southeast this boundary
moves by Thursday morning. Based on the weaker 85h flow and an
inverted trough forming Wednesday evening, precipitation is
likely for the southeastern 1/3 of MPX forecast area through
Thursday morning.

Chances of precipitation diminish considerably by Thursday morning
as the main upper level system moves off to the southeast, and a
drier northeast flow develops. There could be residual showers or
thunderstorms along the Minnesota/Iowa border Thursday afternoon
depending upon the amount of instability leftover from the surface

This drier northeast flow has allowed for a drier forecast on
Friday and Saturday before winds shift to the southeast Saturday
night/Sunday. Dew points drop into the 50s/60s with this northeast
flow which will keep humidity levels comfortable.

Past Sunday, models have continued the trend of a much warmer and
humid air mass returning to the Upper Midwest. This scenario is
likely based on a strong long wave trough building southward
across the Pacific Northwest, which will allow for the Upper Ridge
to build northeast across the Rockies/Northern Plains. Although
both the GFS/EC become more progressive late next week in terms
of a fast west to east flow, I don`t necessary believe in this
scenario, or at least the speed of the change. As it is beyond the
7 day period, and not in the current forecast, will see how things
develop as the upper level pattern evolves.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1225 PM CDT Tue Jul 26 2016

Immediate concern is the convective threat during the period.
Confidence continues to remain highest across central MN into west
central WI this afternoon and evening as the cool front settles
south into the area overnight. Activity over South Dakota is
expected to shift east southeast and move into southwest MN later
tonight into Wed morning as well. Its still a question how far
this activity moves during the morning. SW winds 10-15 knots and
becoming more sly and into the evening...then more e-se into Wed.

KMSP...We continue to expect main convective threat to remain
north and west of the airport through tonight. We may see activity
work into the region Wednesday morning ahead of the next
wave...and continue through the afternoon. Confidence low enough
of timing to just mention vcsh at 17z for now.

Wed ngt...Mainly VFR. CHC MVFR/TSRA. Winds S 5 kts.
Thu...Mainly VFR. CHC MVFR/TSRA. Winds NE 5 kts.
FRI...Mainly VFR. CHC MVFR/TSRA. Winds E 5 kts.


.MPX Watches/Warnings/Advisories...


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